Conventionally, there is known a fuel injection valve having fuel nozzle holes, which are inclined further on an outer peripheral side from a fuel inlet toward a fuel outlet. The fuel nozzle holes are formed and arranged at a valve housing in its circumferential direction. This fuel injection valve opens or closes the fuel nozzle holes through reciprocation movement of a valve member accommodated in the valve housing to perform or stop fuel injection through the fuel nozzle holes.
In a fuel injection valve described in, for example, JP-A-H08-277763, fuel nozzle holes arranged with a common pitch on a common imaginary circle have a common shape around hole axes which are inclined relative to the central axis of a valve housing on the same longitudinal section. As a result of such a configuration, facility in formation of the fuel nozzle holes is increased, and atomization of a spray of fuel injected through each of these fuel nozzle holes is achieved.
In the fuel injection valve of JP-A-H08-277763, inclination angles of the hole axes relative to the central axis are common for each fuel nozzle hole. In this case, for example, when diameter of the fuel nozzle hole is increased or the number of fuel nozzle holes is increased, the pitch between the fuel nozzle holes which are adjacent in a circumferential direction of the valve housing is reduced, and a distance between sprays of fuel injected through these fuel nozzle holes is decreased. As a result, particle diameter of the spray is made coarse because of collision and interference between the sprays of fuel through the adjacent fuel nozzle holes. This coarsening of particle diameter of the spray increases a time required for fuel vaporization to make it difficult to form air-fuel mixture, so that performance of an internal combustion engine may be reduced.
In the fuel injection valve in, for example, JP-A-H08-277763, a pitch circle passing through all the fuel nozzle holes is defined. Based on this definition, the sprays of fuel injected through the adjacent fuel nozzle holes on the pitch circle easily collide and interfere with each other, so that the coarsening of particle diameter of the spray is caused. Accordingly, the atomization of the fuel spray becomes difficult.
For this reason, in a fuel injection valve described in JP-A-H11-070347, an outer imaginary circle passing through outer nozzle holes serving as fuel nozzle holes, and a inner imaginary circle passing through inner nozzle holes serving as fuel nozzle holes radially inward of the outer imaginary circle, are concentrically defined. Based on this definition, the outer nozzle holes and inner nozzle holes are arranged alternately in a circumferential direction of a valve housing so as to be located adjacent to each other between the outer imaginary circle and the inner imaginary circle. Sprays of fuel injected through the outer nozzle holes and the inner nozzle holes which are adjacent as described above do not easily collide and interfere with each other. As a result, the coarsening of particle diameter of the spray can be limited, and the atomization of the fuel spray is thereby made possible.
However, in the fuel injection valve of JP-A-H11-070347, due to a large radial distance between the outer imaginary circle and the inner imaginary circle, attracting force because of the Coanda effect becomes small between the sprays of fuel injected through the outer nozzle holes and the inner nozzle holes which are adjacent to each other. Consequently, it becomes difficult to control penetration (penetrating force) of the fuel spray.
Moreover, in the fuel injection valve in JP-A-H11-070347, because the radial distance between the outer imaginary circle and the inner imaginary circle is large, there is caused a great difference in a fuel flow on an upstream side of a fuel inlet between the outer nozzle holes and the inner nozzle holes. Accordingly, there is caused a great difference also in particle diameter of the sprays of fuel injected through the outer nozzle holes and the inner nozzle holes, which prevents the atomization of the fuel spray.